1. Field of the Invention
The present invention relates to a floating magnetic head slider which shows improved wear resistance without adversely affecting the characteristics of the magnetic head and which is prevented from sticking.
2. Description of the Prior Art
Presently, the contact/start and stop (CSS) system is often used in the floating magnetic heads of hard disk drives, because the CSS system makes the structure simple and reduces the cost. In this CSS system, when a disk is rotating at a high speed, the magnetic head is made to float about 0.1 to 0.3 .mu.m off the surface of the disk. When the rotation of the disk is brought to a stop, the sliding surface of the head is pressed against the surface of the disk. This stationary condition is then maintained. Therefore, when the disk is started and stopped, large frictional forces are produced between the disk and the magnetic head. It is normally desired that the coefficient of friction occurring at this time be set less than 1.
One conventional countermeasure taken to avoid the wear between the magnetic head and the disk surface is to form a very hard film made of SiO.sub.2 or graphite oil the surface of the magnetic disk. Another prevailing countermeasure is to form a lubricating film on the surface of the magnetic disk. The present situation is that almost no countermeasure is taken to protect the magnetic head against wear.
Japanese Patent Laid-open No. 61163/1986 discloses a magnetic head slider having a protective film of carbon on its surface, for protecting the slider against wear. Japanese Patent Publication No. 276074/1990 discloses a magnetic head slider whose surface is made uneven to reduce the coefficient of friction.
In the above-described prior art techniques, the hardness of a magnetic head whose wear resistance is not improved is lower than that of a disk having improved wear resistance. Where they differ greatly in hardness in this way, the magnetic head of a lower hardness is worn away by the surface of the disk, thus producing particles. This increases the coefficient of friction t, which in turn increases the possibility of a head crash. Where the surface is made uneven to reduce the area of frictional contact, if the disk surface and the uneven surface differ greatly in hardness, then problems take place in the same way as in the case of the use of a hard film of graphite described above.
The sliding surface of a slider using a ferrite or calcium has the following problems. In recent years, the recording densities of magnetic heads have tended to be increased. With this trend, heads are made to float a less distance above the disk. Also, disks on which metals are sputtered have been increasingly adopted. In this way, the wear resistances of the sliding surfaces of sliders have been required to be improved further. Experiments were made on sliders made of ferrite as well as on sliders made of calcium. It was confirmed that when the number of CSS tests reached several thousands to tens of thousands, the coefficient of friction exceeded 1, scratching the disk surfaces. Also, head crashes occurred. In this manner, these drives are not satisfactorily reliable.
One contemplated countermeasure taken to reduce the coefficient of friction between the sliding surface of the slider and the disk is to make both surfaces specular. Where the contact/start and stop system is adopted, the magnetic head is pressed against the surface of the disk when the disk stops. If the head is kept at rest for a long time, they are stuck on each other. This phenomenon is known as sticking. Also, when the drive is set into operation, the flexure that holds the magnetic head is deformed or the disk surface is scratched.
A so-called head-loading mechanism is presently available to prevent the aforementioned sticking, in which, when the drive is stopped, the magnetic head is raised from the disk. Unfortunately, this mechanism is complex in structure and expensive to fabricate. Recently, hard disk drives of smaller diameters have been installed in lap top computers. In this case, there is a possibility that magnetic heads are used under severer mechanical environments than conventional desktop computers. Moreover, the number of CSSes tends to be increased because of the adoption of so-called sleep mode, wherein, when data is not accessed, the rotation of the disk is stopped to save the electric power consumed.